Position adjusting drive unit

ABSTRACT

The position adjusting drive unit for a sewing machine having its work shaft driven by an electromotor with an adjustable rotary speed, includes a supporting box connected to the electromotor and including a power supply transformer and an activation mechanism for a signal generator for desired and actual values of the rotary speed of the motor and of the angular position of the working shaft; an exchangeable printed circuit board supports all electrical and mechanical component parts of the speed regulating and angular position adjusting circuits including the signal generators and the coupling rod between the activation mechanism in the supporting box and the part of the activation mechanism on the circuit board is guided into the proper coupling position when the circuit board is electrically connected to the power supply transformer.

This is a continuation of application Ser. No. 167,325, filed July 10,1980, now U.S. Pat. No. 4,393,343.

BACKGROUND OF THE INVENTION

This invention relates in general to driving units for work spindles,and in particular to a position adjustable drive unit having a drivingmotor with adjustable rotary speed for use particularly in connectionwith sewing machines; the unit includes a regulator or controllingsubunit which is provided with generators for producing signalscorresponding to the actual rotary speed value and to the desired rotaryspeed value of the driving electric motor as well as to the actualposition and to the desired position of the work spindle.

The position controlling drive units of this type are known, forexample, from the U.S. Pat. Nos. 3,487,438, 3,532,953, 3,761,790, and4,011,490.

In the following description, the position adjusting drive unitaccording to this invention will be explained in connection with anindustrial sewing machine. It will be understood, however, that thisunit can be readily adapted for numerous other adaptations, for example,for driving machine tools, winding machines for electrical capacitors,and the like. In industrial sewing machines which are also counted amongmachine tools and related products of the machine industry, a continuousincrease of electronic components in the adjustable power drive unitscan be observed in recent designs. This development, however, causesconsiderable problems for final users inasmuch as the maintenance andservicing of such machines is traditionally done by mechanics intraining who, even if experienced in the field of mechanics, usuallyhave no skill in the field of electronics. From this point of view, theeasiness to service and repair the position adjustable drive units insuch machines is of particular importance.

SUMMARY OF THE INVENTION

It is, therefore, a general object of the present invention to providean improved position adjustable drive unit for machine tools which inthe case of a failure can be repaired not only by a mechanic who isuntrained in electronics but also by persons without any technicalskills such as, for instance, an operator of the sewing machine.

In keeping with this object, and others which will become apparenthereafter, one feature of the invention resides in the provision of animproved position adjusting drive unit provided with a drivingelectrical motor having an adjustable rotary speed, an electrical speedregulator for the motor, a generator for producing electrical signalscorresponding to an actual value and to a desired value of the rotaryspeed of the electromotor, an electrical position adjuster including agenerator for producing signals corresponding to an actual position andto a desired position of the driving shaft of the machine, and a commoncircuit board detachably connected to the motor and supporting andinterconnecting the component parts of the speed regulator and theposition adjuster.

Such an arrangement offers an essential advantage in the fact that uponthe occurrence of a failure in the electronics of the drive unit, it isnecessary only to exchange the old circuit board for a new one. Due tothe fact that the circuit board includes the entire speed regulatingcircuit and the position adjusting circuit, it suffices to employ asimple connector without unsoldering or soldering complicated cabletrunks. Any circuit testing during this exchange is completelyeliminated. As a consequence, the replacement of the circuit board canbe made by any untrained person.

The combination of the rotary speed regulating circuit and of theangular position adjusting circuit on a single circuit board hasadditional advantages from the manufacturing point of view.Particularly, by using a printed circuit board all solder points aremade simultaneously in a machine without the use of manual operations.In this manner, not only the aforementioned cable loops forinterconnecting the individual component parts of the rotary speedregulator and of the angular position adjuster are dispensed with butalso cold solder connections which frequently occur during the manualsoldering work are effectively eliminated. For this reason, theoperational reliability is essentially increased and the overallmanufacturing costs are favorably influenced.

In a further elaboration of this invention, the circuit board alsosupports and interconnects a connecting plug for the desired value andthe actual value generators and if needed, additional subunits. The useof connectors for the desired value generators in the circuits of therotary speed regulator and the position adjuster has the advantage ofeasier removal of disturbances which might occur in the desired valuegenerator.

Preferably, the circuit board is insertable into a case or boxcontaining a power supply transformer and connector parts matching thoseon the circuit board. In principle, it is also possible to include thepower supply transformer into the circuits formed on the circuit boardbut, as known from practice, the defects in power transformance occur sorarely that for the subsequent service the probability for thereplacement of the power transformer is so small that it candisregarded. Moreover, by installing the power supply transformer in theconnector box of the unit, the finished circuit board has a relativelylow weight and a flat configuration, which features are advantageous notonly for manufacture but also for transportation and storing of thereplacement boards.

The connector box further includes an activation device for the desiredvalue generator which is mounted on the circuit board. Upon theinsertion of the circuit board into the box, an activation rodprojecting from the generator is automatically coupled to the activationunit. In this manner, a correct coupling of the desired value generatorto its control mechanism such as, for example, a hand operated linkage,is always insured after the exchange of the circuit board.

The basic circuit board can also be provided with additional plug-inconnectors for one or more additional circuit boards. The additionalcircuit boards can be used, for example, for adjusting the rotary speedregulator and the position adjuster to different types of the drivenmachine. In particular, the additional circuit boards include controlcircuits for one or more additional functions of the work machine andmore particularly of an industrial sewing machine, incorporating thedriven shaft. The additional control circuits may include, for instance,a rotary speed limiting stage, a stage for presetting a desired rotaryspeed of the thread cutter, a stage for controlling a predeterminedcourse of the high rotary speed of the machine (for example, for alinear, square or exponential increase of the rotary drive in the rangeof high speeds), furthermore the stages for severing and/or wiping ofthe threads, for relieving the tension of the thread, the activation ofthe press shoe and the feed reversal (in the forward or backwarddirection), a stage for arresting the stitches, a stage for controllingthe length of the stitches or a stage for checking of additional signalgenerators employed in the sewing machine such as, for example, lightbarriers for detecting the beginning and the end of the fabric.

All connecting sockets and setting potentiometers are preferablysoldered simultaneously with the remaining connection points in thecircuits present on the circuit board in order to avoid manual solderingoperation and cable connections.

In another modification of this invention, the rotary speed regulatorand the angular position adjuster supported on the circuit board arepreferably in the form of integrated circuits operating asmicroprocessor systems. Such systems are not only of extremely lowweight and space saving, but also enable a versatility of matching tospecial application requirements. The microprocessor system can includeone or more integrated circuit chips.

The desired value generator includes preferably a light barrier with acorresponding aperture plate or diaphragm. Such a signal generator has avery small size and therefore is particularly suitable for installationon the circuit board. The light barrier and its aperture plate can bedesigned as an analog signal generating system. According to a furtheradvantageous development of this invention, the desired value signalgenerator, however, is equipped with several light barriers and withcorrespondingly coded aperture plates for generating a digital signal ofthe desired value of the rotary speed. Such a digitally coded signal canbe exactly and directly processed in the microprocessor system. Astepped signal corresponding to the desired value of the rotary speedfurther enables to bypass the resonant points resulting during therotation of the driven shaft in the working machine so that theresonance phenomena technically remain without any disturbing effect.The light barriers eliminate any mechanical contacts or sets ofcontacts. Generally, it is advantageous when the signal for the desiredrotary speed is combined into a common structural unit with the signalgenerator for the actual position of the shaft.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the position adjusting drive unit ofthis invention shown without the circuit board;

FIG. 2 is a top view of a circuit board for the unit of FIG. 1;

FIG. 3 is a side view of the circuit board of FIG. 2 viewed in thedirection of arrows III;

FIG. 4 is a side view of the circuit board of FIG. 2 viewed in thedirection of arrows IV;

FIG. 5 is a cutaway perspective view of the unit of FIG. 1 shown withthe activating mechanism for the desired value signal generator;

FIG. 6 is a perspective view of a cutaway portion of the circuit boardwith a group of light barriers;

FIG. 7 is a side view partly in section of a signal generator for thedesired value of the rotary speed;

FIG. 8 is a top view of the signal generator of FIG. 7;

FIG. 9 is a sectional side view of a slider of the signal generator ofFIG. 8 taken along the line IX--IX;

FIG. 10 is a sectional side view of the slider of FIG. 9 taken along theline X--X;

FIG. 11 is another sectional side view of the slider of FIG. 9 takenalong the line XI--XI; and

FIG. 12 is a side view of an aperture or stop plate connected to theslider of FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIG. 1, there is depicted schematically a drivingelectrical motor 1 of the type having a controllable rotary speed. Asupporting contact box 2 is united with the motor 1 by means of clampingrings 3. The driving motor 1 is preferably a clutch case motor ofsuitable known construction described, for example, in theaforementioned U.S. patents. A direct current electrical motor havingadjustable rotary speed can also be employed. In the box 2 there arearranged, apart from other non-illustrated component parts, a powersupply transformer 4 for energizing the control circuit for the rotaryspeed and the control circuit for the angular position adjustment of thedriven shaft. The box 2 has an open outer side and is provided with tworeceptacles 5 arranged at the lower edge of the opening and having aU-shaped cross section for receiving projections 6 formed on a printedcircuit board 7, as illustrated in FIGS. 2-4.

The circuit board 7 as indicated in FIG. 2 supports and interconnectsthe component parts of operative circuits of a rotary speed regulatorand of an angular position adjuster for the driving motor. Theseindividual circuits are known from prior art and are described, forexample, in the aforementioned U.S. Pat. Nos. 3,487,438, 3,532,953,3,761,790, and 4,011,490. In addition, the circuit board 7 includes alsoa signal generator 8 for generating a signal corresponding to thedesired value of the rotary speed and of the desired angular position. Aconnector plug 11 is mounted on the board 7 in such a manner that uponthe insertion of the retaining projections 6 into the correspondingreceptacles 5, the pins of the connector plug 11 enter into theconnector socket 12 mounted in the supporting box 2. The connector parts11 and 12 detachably connect the rotary speed controlling circuit andthe angular position adjustment circuit on the common circuit board 7 tothe supply voltage provided by the transformer 4. The upper edge of theboard 7 abuts against surfaces 13 formed on the box 2 and is secured tothe latter by screws passing through holes 14 in the board and engagingscrew holes 15 in the abutment surfaces 13.

The right end wall of the supporting box 2 is formed with a cut out 16for leading through a cable 17 attached to the circuit board 7. In theevent that a coupling or case motor is used as the driving motor 1, thecable 17 is connected to the clutch or brake unit of the motor as wellas to a press pedal control unit for the motor 1 to energize the sewingmachine. Upon the insertion of the circuit box 7 into the supporting box2, connector sockets or sleeves 20 and 21 mounted at a lateral side ofthe board 7 are aligned with corresponding openings 22 and 23 in theright end wall of the box 2. Through the openings 22 and 23 plugs ofadditional non-illustrated cables can be inserted into the connectorcircuits 20 and 21. These additional cables connect the combinedregulating and adjusting circuits on the board 7, for example, to athread cutting system and to an angular position feeler which isoperatively coupled to the top shaft for driving the needle arm todetect the momentary angular position of the top shaft. Similarly, thetrimmer potentiometers 24 which are arranged at the left end of thecircuit board 7 in FIG. 2 are in alignment with openings 25 in the leftend side wall 26 of the box 2 so that the trimming potentiometers areeasily accessible from the outside.

The signal generator 8 for the desired value of the rotary speed as wellas for the desired angular position of the work spindle (top spindle forthe needle arm in the sewing machine) is controlled by an activation pin30 projecting from the left end of the circuit board 7. As is indicatedin FIG. 5, during the installation of the board 7 on the supporting box2, the activation pin 30 enters a slot 31 in a guiding plate 32 of anactivation mechanism which is also arranged inside the box 2. Theguiding plate 32 has a V-shaped configuration defining two divergingguiding surfaces 33 and 34 whereby the coupling slot 31 is formed at theapex edge of these guiding surfaces. In this manner, it is ensured thatthe activation pin 30 during the installation of the circuit board isreliably guided into the slot 31. The guiding plate 32 is secured to anarm 35 of a lever 36 firmly connected to a shaft 37 which at one endthereof is pivotably supported in a bearing block 38. The other end ofthe shaft 37 passes through the lateral wall 26 of the box 2 and is alsorotatably supported thereon. The projecting end of the shaft 37 isconnected to a control lever 39 which in turn is hinged to an adjustmentrod 40. The adjustment rod 40 is linked to a non-illustrated controlpedal. The control arm 39 is also provided with lateral pin 41 whichprojects into a guide slot 42 formed in the lateral wall 26 of the box 2so that the angular displacement of the control lever is limited withinthe range of the guide slot.

Apart from the signal generator 8 for the desired rotational speed, theconnector block 11, the connector sockets 20 and 21, the trimmingpotentiometers 24 and the remaining component parts of the rotary speedregulating circuit and of the angular position adjusting circuit, asindicated schematically in FIG. 2, and which are soldered to a printedcircuit in a single soldering step, the circuit board 7 also supportsone or more connector sockets 44 for plugging in additional orsupplementary circuit boards. Such additional circuit boards can servefor adding supplementary operational functions to the machine. Asmentioned before, the rotary speed regulator and the angular positionadjusters are preferably constructed as a microprocessor system.

The signal generator 8 for the desired value includes a pack ofphotodiodes 47 and a pack of phototransistors 48 arranged on the circuitboard 7 opposite each other with a certain clearance therebetween. Ascan be seen from the perspective illustration in FIG. 6, the pack ofphotodiodes 47 includes four light-emitting diodes 49 acting as lighttransmitters. Each light-emitting diode faces a phototransistor actingas a light receiver and forming with the light-emitting diode a lightbarrier. In this manner, the signal generator 8 is formed with fourlight barriers. Packs 47 and 48 project, respectively, into chambers 51and 52 (FIG. 10) of a slider 53 which is movable in its longitudinaldirection on the circuit board 7. The chambers 51 and 52 are separatedby an intermediate partition 54 extending over a portion of theirlongitudinal dimension and, as seen from FIG. 9, the free edge 55 of thepartition is stepped. The individual steps of the edge 55 are levelledwith respective light barriers. The slider 53 is provided with adownwardly directed guiding pin 56 cooperating with a guide slot 57(FIG. 6) in the circuit board 7. An upwardly projecting extension 58formed on the slider 53 is provided with an activation pin 30 which isguided in an oblong slot 60 formed in a guiding part 61 which is rigidlyconnected to the board 7 (FIGS. 7-9). The end face of the slider 53remote from the intermediate partition 54 is formed with a bore 62 intowhich is forced the end of a guiding rod 63. The free end of the guidingrod 63 passes through an elongated bore 64 of the guiding part 61 and issupported therein for a sliding movement in slide bearings 65 and 66. Astep plate 68 is rigidly connected to the slider 53 and is aligned inthe longitudinal direction of the slider with the intermediate partition54. An upwardly directed projection 69 of the stop plate 68 passesthrough a slot 70 in the upper wall 71 of the slider 53; the projection69 is formed with a hole 72 for retaining pin 73 which is anchored inthe upper wall 71 of the slider 53 and releasably connects the stopplate 68 to the slider. The stop plate 68 is formed with four stopapertures 76, 77, 78, and 79 arranged at the levels of respective lightbarriers in the packs 47 and 48; the edge of the stop plate facing thestepped edge of the intermediate partition 54 is formed withcomplementary steps 80 which are again levelled with the respectivelight barriers. The steps 80 at the edge of the stop plate all togetherwith the steps 55 at the opposite edge of the intermediate partition 54define therebetween additional stop apertures. In adjusting the positionof the slider 53 and of the stop plate 68 by means of the activation pin30, the light barriers in an alternating combination are eitheruninterrupted or interrupted. The stop apertures 76-79 as well as theadditional stop apertures delimited by the stepped edges 55 and 80 canbe designed for blocking according to a Gray code. By activating thepedal and the corresponding displacement of the adjustment rod 40,several values, for example, twelve desired values of the rotary speedcan be selected, whereas by activating the pedal rearwards signalscorresponding to the desired holding angular position of the work shaftis reversed from "needle up" to "needle down" or vice versa. The stepsof the desired rotary speed can be simply selected so that, for example,in view of the resonance phenomena of the machine the undesired rangesof the rotary speed can be omitted.

During the assembly of the drive unit of this invention, the circuitboard 7 is first attached to the box 2. In doing so, the connector plug11 enters automatically the connector socket 12 and the electricalconnection between the circuit board 7 and the power supply circuit inthe box 2 is established, that means, electrical connection of therotary speed regulator and the angular position adjuster is electricallycoupled to the power supply transformer 4. Without any additionalmanipulation, as soon as the circuit board is applied against the openside of the box 2, the mechanical connection between the activation rod30 of the signal generator 8 and the adjustment rod 40 is completed.Thereupon, the board is fastened to the box 2 by screws engaging thethreaded bores 82 and covered by a non-illustrated covering member.

If a failure occurs in the electronics of the drive unit of thisinvention, it is no longer necessary to locate the trouble bytime-consuming measurements which can be made only by a specialist. Itis only necessary to exchange a spare circuit board 7 for the defectiveone whereby all mechanical and electrical connections are madeautomatically in the aforedescribed manner.

The drive unit of this invention is applicable for a great variety ofmachine tools such as, for example, sewing machines. In particular, allor a major portion of the existing types of sewing machine can beequipped with a standard driving motor 1 and a standard box 2 whereasthe matching of the motor to the particular machine is made by theaforementioned additional circuit boards connectable to the basiccircuit board 7. The motor 1 and the control box 2 can be economicallymade in large production series and held in store. In order to fulfilldifferent application requirements, it is only necessary to employ thesupplementary circuit boards in addition to the basic circuit board 7.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofconstructions differing from the type described above.

While the invention has been illustrated and described as embodied in adrive unit for use with sewing machines, it is not intended to belimited to the details shown, since various modifications and structuralchanges may be made without departing in any way from the spirit of thepresent invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or the specific aspects of thisinvention.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.
 1. A position adjusting drive unit fora rotary shaft of a sewing machine, comprising a driving electricalmotor having an adjustable rotary speed, an electrical speed regulatingcircuit for said motor, an electrical angular position adjusting circuitfor the rotary shaft of the machine, operator-adjustable means connectedto said circuits for generating signals corresponding to desired valuesof the rotary speed and of the angular position, means connected to saidcircuit for generating signals corresponding to actual values of therotary speed and of the angular position, a circuit board supporting andinterconnecting the electrical and mechanical component parts of saidcircuits and of said operator-adjustable signal generating means andsupporting connectors for connecting said means for generating signalscorresponding to actual values of the rotary speed and of the angularposition, one of said mechanical component parts being an activationmechanism for said means for generating signals corresponding to desiredvalues of said rotary speed and of said angular position, and asupporting box mechanically attached to said motor and having means fordisconnectably supporting said circuit board, said supporting boxfurther including a complementary activation device having guiding meansfor guiding and coupling said activation mechanism when said circuitboard is attached to said supporting box.
 2. A drive unit as defined inclaim 1, wherein said circuit board supports additional connectors forconnecting external supplementary operating means.
 3. A drive unit asdefined in claim 1, wherein said circuit board includes additionalconnector sockets for connecting at least one auxiliary circuit board.4. A drive unit as defined in claim 3, wherein said auxiliary circuitboards support and interconnect control circuits for additionaloperational functions of the driven machine.
 5. A drive unit as definedin claim 2, further including trimming potentiometers mounted andinterconnected in the circuits on said board.
 6. A drive unit as definedin claim 1, wherein said rotary speed regulating circuit and saidposition adjusting circuit are in the form of a microprocessor system.7. A drive unit as defined in claim 9, wherein said microprocessorsystem includes at least one integrated circuit chip.
 8. A positionadjusting drive unit for a rotary shaft of a sewing machine, comprisinga driving electrical motor having an adjustable rotary speed; anelectrical speed regulating circuit for said motor; an electricalangular position adjusting circuit for the rotary shaft of the machine;operator-adjustable means connected to said circuits for generatingsignals corresponding to desired values of the rotary speed and of theangular position; means connected to said circuit for generating signalscorresponding to actual values of the rotary speed and of the angularposition; a common circuit board supporting and interconnecting theelectrical and mechanical component parts of said circuit and of saidoperator-adjustable signal generator means, said board being providedwith connectors for connecting said means for generating signalscorresponding to actual values of the rotary speed and of the angularposition, and with a power supply connector plug; one of said mechanicalcomponent parts being an activation mechanism for said means forgenerating signals corresponding to desired values of said rotary speedand of said angular position; a supporting box mechanically attached tosaid motor and having circuit board supporting means for disconnectablysupporting said circuit board, said supporting box further including acomplementary activation device having guiding means for guiding andcoupling said activation mechanism when said circuit board is attachedto said supporting box; and a power supply transformer provided with aconnector socket matching said connector plug.